This invention pertains to the art of fuel-burning devices and, more particularly, to a fuel-burning device including an oxidation catalyst.
The invention is particularly applicable to woodburning stoves. The invention can be readily used in other fuel burning appliances in which an oxidation catalyst is employed, particularly in other solid fuel appliances.
Conventional woodburning stoves, fireboxes or fireplaces do not burn all the combustible substances of a conventional fuel such as wood. The smoke and gas effluent of a wood fire normally contains creosotes and substantial quantities of oxidizable substances such as combustible gases. Such gases can condense and become attached to a flue passageway during the emission of the effluent to the environment. Continued condensation and attachment may result in a particularly undesirable fire hazard in a flue or chimney, substantially hampering the efficiency of the burning device, and polluting the atmosphere.
In a wood burning operation, at a temperature of 250.degree. F., oxidizable effluent gases are completely fogged (condensed droplets) while at 450.degree. F. the effluent is 70-80% gas with the remainder comprising condensed droplets. Since the condensed droplets will not oxidize in a catalyst, an effluent reheating method or element has been necessary to raise the temperature of the effluent such that the condensed droplets would again become gaseous. Alternatively, the effluent was kept extremely hot, often by overfiring the stove.
Oxidation catalysts have been employed in combination with other fuel burning or incinerator devices for combusting smoke, creosotic flue gases and other objectionable components in the effluent. In order to promote such combustion, some prior art devices have employed various methods to reheat creosotic gases which have condensed to droplets during travel from the burning fuel to the catalyst.
In other catalytic woodburning stoves found in the prior art, it has been necessary to operate the stove at a temperature higher than was desirable for residential operation, in order to operate the catalyst device without reheating the effluent. Such stoves would often consume six or more pounds of wood per hour in order to prevent some of the effluent from cooling to a temperature near 250.degree. F. and condensing as it passed from the woodburning flame to the catalyst. Substantial eddying of effluent along the stove top and side walls would cause the effluent to cool. To prevent such cooling an undesirably high temperature had to be maintained so that the effluent would contain predominantly gases as opposed to condensed creosote droplets.
The present invention contemplates a new and improved device which overcomes all of the above referred to problems. It provides a new catalytic stove which is simple in design, economical to manufacture and adaptable for use in residential environment. It is easy to install, and it operates at a temperature which is not undesirably hot, unsafe, or wasteful of energy. The present invention provides improved catalytic oxidation of effluent from a burning fuel.
The present invention combines a unique catalytic dome with a uniquely controlled and directed air flow. It typically lowers fuel useage from an objectionable six or more pounds per hour (a burning rate higher than normally encountered in homes) to a heretofore unobtainable two pounds per hour (a rate commonly desired in homes). This economy greatly expands the operating range of a catalytic woodburning stove.